一项关于大肠杆菌异亮氨酰 - tRNA合成酶激活异亮氨酸机制的立体化学和位置同位素交换研究。

A stereochemical and positional isotope exchange study of the mechanism of activation of isoleucine by isoleucyl-tRNA synthetase from Escherichia coli.

作者信息

Lowe G, Sproat B S, Tansley G, Cullis P M

出版信息

Biochemistry. 1983 Mar 1;22(5):1229-36. doi: 10.1021/bi00274a037.

Abstract

Isoleucyl-tRNA synthetase from Escherichia coli catalyzes the activation of [18O2]isoleucine by adenosine 5'-[(R)-alpha-17O]triphosphate with inversion of configuration at phosphorus. Moreover, isoleucyl-tRNA synthetase does not catalyze positional isotope exchange in adenosine 5'-[beta-18O2]triphosphate in the absence of isoleucine or in the presence of the competitive inhibitor isoleucinol, which effectively eliminates the possibility of either adenylyl-enzyme or adenosine metaphosphate intermediates being involved. Together, these observations require that isoleucyl-tRNA synthetase catalyzes the activation of isoleucine by associative "in line" nucleotidyl transfer. The synthesis of adenosine 5'-[(R)-alpha-17O]diphosphate and its conversion to adenosine 5'-[(R)-alpha-17O]triphosphate is described and an explanation provided for the reported differences between the treatment of adenosine 5'-[(S)-alpha-thiodiphosphate] with cyanogen bromide and bromine in [18O]water.

摘要

来自大肠杆菌的异亮氨酰 - tRNA合成酶催化[18O2]异亮氨酸与腺苷5'-[(R)-α - 17O]三磷酸的活化反应，磷原子构型发生翻转。此外，在不存在异亮氨酸或存在竞争性抑制剂异亮氨醇的情况下，异亮氨酰 - tRNA合成酶不会催化腺苷5'-[β - 18O2]三磷酸的位置同位素交换，这有效地排除了腺苷酰 - 酶或腺苷偏磷酸中间体参与的可能性。综合这些观察结果，表明异亮氨酰 - tRNA合成酶通过缔合性“直线型”核苷酸转移催化异亮氨酸的活化反应。文中描述了腺苷5'-[(R)-α - 17O]二磷酸的合成及其转化为腺苷5'-[(R)-α - 17O]三磷酸的过程，并对报道的在[18O]水中用溴化氰和溴处理腺苷5'-[(S)-α - 硫代二磷酸]之间的差异给出了解释。